How can my partner and I ensure a fair divide in our new home?

Q My partner and I are buying a home together which is in need of renovation. We will be contributing unequal shares so how do we each protect our investment but share the profit associated with the renovation? I understand one possibility is to make sure all investments, including renovation costs are split proportionately but in practice, dividing the cost and time of painting a room or a new boiler could become very complex and tedious. I’ll be contributing £240,000, he’ll be contributing £45,000 and we will also have a £36,000 mortgage which we could split or he could take responsibility for in order to up his investment in the property. I know much of these decisions are down to personal choice but I feel uncomfortable with a percentage-based split if we are both investing our time and emotion equally into improving the home. AM

A When two (or more) people buy property together in unequal shares, as you and your partner intend to do, it is advisable to have a “deed of trust” prepared. This legal document sets out how you will own the property, what shares you own the property in and what will happen to your share if you sell it and/or separate. It can also detail how you will split the bills and costs of maintaining the property. You are right in thinking that if, as in your case, you own 80% (assuming you take on half the mortgage) and your partner owns 20%, then you should split renovation costs in these percentages. But you are also right in thinking that could become a bit tedious and that dividing your time and emotion on that basis could be pretty tricky. An alternative approach is to draw up the deed of trust so it says that if you sell the home, you should each get back the amount you put in as a deposit plus 50% of any increase in the value of the property after paying off the mortgage. If your partner were to take full responsibility for paying the mortgage, the trust deed could reflect this by saying that you would get back your deposit and your partner would get back his deposit plus the mortgage amount – but less the amount needed to pay off the outstanding loan on the sale of the property – with each of you getting half of any profit as well. Whichever of these two approaches you take, it simplifies how you split the cost, time and effort you put into the renovation because you simply split them down the middle.

Muddled about mortgages? Concerned about conveyancing? Email your homebuying and borrowing worries to Virginia Wallis at virginia.wallis.freelance@theguardian.com